Stent device having reduced foreshortening and recoil and method of making same

ABSTRACT

A stent device includes generally cylindrical rings aligned along a longitudinal axis, and interconnected by interconnecting members. Each interconnecting member includes a first coupling end, a second coupling end, and an elongate portion therebetween. The first coupling end, the elongate portion, and the second coupling end combine in either a first orientation or a second orientation, which are substantially mirror images. For each interconnecting member, the first coupling end can intersect with a midpoint of a transition region of a substantially repeating curved segment on one of the rings, and the second coupling end can intersect with a midpoint of a curved segment of a different and immediately adjacent ring. The interconnecting members can be arranged in rows extending longitudinally along the device. Along each row, consecutive interconnected members alternate between the first orientation and the second orientation. A cover may be provided over the stent device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/834,250 (filed on Mar. 15, 2013), which is now U.S. Pat. No.10,271,975 (issued on Apr. 30, 2019), both of which are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to expandable, intraluminal devices foruse within a body passageway or duct. More particularly, the presentinvention relates to stent devices exhibiting substantially improvedcharacteristics from known devices in the form of reduced foreshorteningand recoil, and their methods of manufacture.

BACKGROUND OF THE INVENTION

A common method for treating stenosed vessels or other blockedpassageways is to utilize an expandable prosthesis or stent. The stentis delivered to a target site, expanded, and affixed in place. Thedeployed and affixed stent creates an enlarged lumen space for passageof blood and also provides increased reinforcement of the vessel wall,in order to maintain the cleared passageway. Stents can be covered oruncovered. Some existing covered stents provide a series ofinterconnected metal rings encapsulated by a layer of biocompatiblematerial. In uncovered stents (referred to as “bare metal stents”), theseries of interconnected metal rings are exposed directly to the vesseland do not include any sort of cover.

Covered stents are desirable over bare metal stents in manycircumstances as they provide more uniform coverage (e.g., gaps betweenstent struts are not exposed to walls of the target site, etc.) andimproved luminal patency over bare metal stents in addition to otherbenefits. However, covered stents suffer from some operationalshortcomings like foreshortening and recoil. In contrast, many baremetal stents exhibit little to no foreshortening and minimal recoil whendeployed. Yet, the very same stents often will foreshorten by up totwenty five percent or more when deployed with a cover. However, in someinstances, covered stents outperform bare metal stents in freedom fromrestenosis within particular defined periods of time (e.g., during thefirst 18 months following stent implantation).

For example, FIG. 1 depicts one example of a known stent design for aconventional covered stent 110 (cover not shown for clarity). The stent110 is depicted in a flattened, discontinuous state for purposes ofillustration. The stent 110 includes a series of rings 112, which inactuality are generally cylindrical and continuous at their ends (i.e.,connected at the tops and bottoms). The rings 112 are generallycylindrical and aligned in a series. Each ring 112 is generally made upof a plurality of repeating peaks and valleys 114 a, 114 b. In theexample stent 110 of FIG. 1, each particular ring 112 is a mirror imageof any ring 112 adjacent to it in the series. Accordingly, for any twoadjacent rings 112, the peaks 114 a of one ring 112 arecircumferentially aligned with the valleys 114 b of the other ring 112,and vice versa. Each iteration of a peak 114 a and a valley 114 b formsa repeating bent segment 122. The rings 112 fixedly secured to oneanother by a plurality of interconnecting members 116. Eachinterconnecting member 116 includes two elbows 118 and an elongateportion 120 disposed therebetween.

In general, each interconnecting member 116 can occupy any one of anumber of different configurations. In an “up-up” or “down-down”configuration, the elbows 118 of a single interconnecting member 116extend to the same side (e.g., to the top or the bottom, respectively)of the elongate portion 120. Said differently, in an “up-up”confirmation or a “down-down” configuration, the elbows 118 of a singleinterconnecting member 116 extend circumferentially in the samedirection (e.g., clockwise or counterclockwise). On the other hand, inan “up-down” or “down-up” configuration, the two elbows 118 of a singleinterconnecting member 116 extend to different sides (e.g., to the topand the bottom, or to the bottom and the top, respectively) of theelongate portion 120.

In the example of FIG. 1, each of the interconnecting members 116 iseither in a “down-up” configuration or an “up-down” configuration. Thisis a conventional and prevailing design for many known stents.Additionally, in the example stent 110 of FIG. 1, there are half as manyinterconnecting members 116 disposed between any two adjacent rings 112as there are repeating bent segments 122 in any single ring 112. Thistoo is a common design feature for known stents. The stent 110 includesa cover (not shown, for clarity). The cover can be constructed from abiocompatible material (not shown) such as expandedpolytetrafluoroethylene (ePFTE).

As described above, the conventional stent 110 is often associated withoperational drawbacks, including foreshortening and recoil, especiallywhen covered. Foreshortening is the property of a stent decreasing inlength during expansion. Recoil is the property of a stent contractingfrom an expanded diameter to a partially expanded or non-expandeddiameter. Foreshortening is particularly problematic, as it compromisesthe ability of the stent 110 to ensure correct placement and treatmentof the stenosed vessel, and it also increases risk of damage tosurrounding intima during expansion. Furthermore, recoil is associatedwith other risks, such as reduced reinforcement, which can lead togreater occlusion and blockage of the affected passageway. In general,poor efficacy of covered stents (e.g., as caused by substantial quantityof foreshortening and substantial quantity of recoil) has been proven inclinical settings to be linked with higher risk of restenosis. Thus, fora stent to be operable and safe for use, these negative characteristicsmust be eliminated, or at least maintained at acceptably low levels.

SUMMARY

There is a need for a stent device capable of being covered and havingreduced foreshortening and recoil characteristics. The present inventionis directed toward solutions to address this need, in addition to havingother desirable characteristics that will be appreciated by one of skillin the art upon reading the present specification.

In accordance with an example embodiment of the present invention, astent device is provided. The stent device includes a plurality ofgenerally cylindrical rings each formed by a plurality of substantiallyrepeating bent segments. Each of the plurality of bent segments includesone substantial peak, one substantial valley, and a transition regionleading between the one substantial peak and the one substantial valley.Each bent segment has a midpoint on the transition region substantiallymidway between the one substantial peak and the one substantial valley.The plurality of rings are arranged in a series along a longitudinalaxis in such a way that the one substantial peak and the one substantialvalley of each bent segment of each ring in the series is substantiallya mirror image of one substantial peak and one substantial valley of acorresponding curved segment in an immediately adjacent ring. Aplurality of interconnecting members are included in the stent device,and each of the plurality of interconnecting members includes a firstcoupling end and a second coupling end opposite the first coupling end.An elongate portion extends between the first coupling end and thesecond coupling end. The first coupling end, the elongate portion, andthe second coupling end combine in a first orientation or a secondorientation that is substantially a mirror image of the firstorientation. The first coupling end intersects with the midpoint of thetransition region of a bent segment of a ring of the plurality of ringsand the second coupling end intersects with the midpoint of a bentsegment of a different and immediately adjacent ring of the plurality ofrings. The plurality of interconnecting members are arranged in rowsextending longitudinally along the device. Along each of the rows theinterconnecting members alternate with each consecutive occurrencebetween the first orientation and the second orientation. The stentdevice further includes a cover disposed on the plurality of cylindricalrings and the plurality of interconnecting members.

In accordance with aspects of the present invention, the first couplingend and the second coupling end of each of the plurality ofinterconnecting members each can include an elbow. The number ofinterconnecting members between any two adjacent rings of the pluralityof rings can be equal to the number of substantially repeating bentsegments in each ring of the plurality of rings. The first coupling endand the second coupling end of each of the plurality of interconnectingmembers can be azimuthally aligned. The first coupling end and thesecond coupling end of each of the plurality of interconnecting memberscan be circumferentially aligned. Each of the plurality of rings can beindependently expandable in a radial direction. The plurality ofsubstantially repeating bent segments can form a generally sinusoidalpattern. A peak-to-valley amplitude quantity can be substantially equalfor each of the plurality of rings. Each of the plurality of bentsegments can have a substantially uniform width. All of the plurality ofbent segments have substantially the same substantially uniform width.One or more of the plurality of interconnecting members can have asubstantially non-uniform width.

In accordance with aspects of the present invention, the cover caninclude one or more cover materials, one or more coatings, or both. Thecover can substantially cover an entirety of the plurality of rings. Thecover can include expanded polytetrafluoroethylene (ePTFE). Theplurality of rings can be constructed from one or more of anon-biodegradable alloy, stainless steel, or cobalt chromium. When thestent device with cover is expanded up to an operational deploymentdiameter, the stent device can exhibit a foreshortening of about 6% orless, about 3% or less, about 2% or less, about 1% or less, or about 0%or less. The stent device with cover can exhibit a foreshortening ofabout 0% when expanded up to an operational deployment diameter. Thestent device with cover can exhibit a recoil of about 6.6% or less whenthe stent device with cover has an initial diameter of 1.6 mm and anexpanded diameter of 5 mm. The stent device with cover can exhibit arecoil of about 7% or less when the covered stent has an initialdiameter of 1.7 mm and an expanded diameter of 6 mm. The stent devicewith cover can exhibit a recoil of about 6.7% or less when the stentdevice with cover has an initial diameter of 1.8 mm and an expandeddiameter of about 7 mm.

In accordance with an example embodiment of the present invention, astent device is provided. The stent device includes a stent including aplurality of radially expandable rings arranged in a series along acommon longitudinal axis and coupled together by a plurality ofinterconnecting members. Each of the plurality of radially expandablerings includes a plurality of substantially repeating bent segments. Acover formed of expanded polytetrafluoroethylene and including an innerlayer and an outer layer can encapsulate the stent. When expanded to anoperational deployment diameter, the stent device and cover can exhibitforeshortening of about 6% or less.

In accordance with aspects of the present invention, the stent devicewith cover can exhibit foreshortening of about 3% or less when expandedto an operational deployment diameter. The stent device with cover canexhibit foreshortening of about 2% or less when expanded to anoperational deployment diameter. The stent device with cover can exhibitforeshortening of about 1% or less when expanded to an operationaldeployment diameter. The stent device with cover can exhibitforeshortening of about 0% or less when expanded to an operationaldeployment diameter.

In accordance with an example embodiment of the present invention, amethod of manufacturing a stent device includes providing a plurality ofgenerally cylindrical rings each formed by a plurality of substantiallyrepeating bent segments. Each of the plurality of bent segments includesone substantial peak, one substantial valley, and a transition regionleading between the one substantial peak and the one substantial valley.Each bent segment has a midpoint on the transition region substantiallymidway between the one substantial peak and the one substantial valley.The plurality of rings are arranged in a series along a longitudinalaxis in such a way that the one substantial peak and the one substantialvalley of each bent segment of each ring in the series is substantiallya mirror image of one substantial peak and one substantial valley of acorresponding curved segment in an immediately adjacent ring. Aplurality of interconnecting members are provided, and each of theplurality of interconnecting members including a first coupling end, asecond coupling end opposite the first coupling end, and an elongateportion extending between the first coupling end and the second couplingend. The first coupling end, the elongate portion, and the secondcoupling end combine in a first orientation or a second orientation thatis substantially a mirror image of the first orientation. A cover can bedisposed on the plurality of cylindrical rings and the plurality ofinterconnecting members. The first coupling end intersects with themidpoint of the transition region of a bent segment of a ring of theplurality of rings and the second coupling end intersects with themidpoint of a bent segment of a different and immediately adjacent ringof the plurality of rings. The plurality of interconnecting members isarranged in rows extending longitudinally along the device. Along eachof the rows, the interconnecting members alternate with each consecutiveoccurrence between the first orientation and the second orientation.

In accordance with further aspects of the present invention, the firstcoupling end and the second coupling end of each of the plurality ofinterconnecting members each can include an elbow. The number ofinterconnecting members between any two adjacent rings of the pluralityof rings can be equal to the number of substantially repeating bentsegments in each ring of the plurality of rings. The first coupling endand the second coupling end of each of the plurality of interconnectingmembers can be azimuthally aligned. The first coupling end and thesecond coupling end of each of the plurality of interconnecting memberscan be circumferentially aligned. Each of the plurality of rings can beindependently expandable in a radial direction. The plurality ofsubstantially repeating bent segments can form a generally sinusoidalpattern. A peak-to-valley amplitude quantity can be substantially equalfor each of the plurality of rings. Each of the plurality of bentsegments can have a substantially uniform width. All of the plurality ofbent segments can have substantially the same substantially uniformwidth. One or more of the plurality of interconnecting members can havea substantially non-uniform width.

In accordance with further aspects of the present invention, the covercan substantially cover an entirety of a length of the plurality ofrings. The cover can include expanded polytetrafluoroethylene (ePTFE).The cover can include one or more cover materials, or one or morecoatings. The plurality of rings can be constructed from one or more ofa non-biodegradable alloy, stainless steel, or cobalt chromium. Thestent device with cover can be expanded up to an operational diameterthen the stent device exhibits a foreshortening of about 6% or less,about 3% or less, about 2% or less, about 1% or less, or about 0% orless. The stent device with cover can exhibit a foreshortening of about0% when expanded up to an operational diameter.

In accordance with an example embodiment of the present invention, astent device is provided. The stent device includes a stent thatincludes a plurality of radially expandable rings arranged in a seriesalong a common longitudinal axis and coupled by a plurality ofinterconnecting members. Each of the plurality of radially expandablerings includes a plurality of substantially repeating bent segments. Thestent device can include a cover formed of expandedpolytetrafluoroethylene. The cover includes an inner layer and an outerlayer, and the cover encapsulates the stent. The stent device with coverexhibits foreshortening as indicated by a foreshortening curve shown inFIG. 7 or a foreshortening regime lying below a foreshortening curveshown in FIG. 7.

In accordance with aspects of the present invention, the stent can havea length of about 24 mm or about 16 mm, and the stent device with covercan exhibit foreshortening as indicated by one of the foreshorteningcurves shown in FIG. 7.

In accordance with aspects of the present invention, a stent device isprovided that includes a plurality of radially expandable rings coupledtogether by a plurality of interconnecting members arranged as shown inFIG. 3.

BRIEF DESCRIPTION OF THE FIGURES

These and other characteristics of the present invention will be morefully understood by reference to the following detailed description inconjunction with the attached drawings, in which:

FIG. 1 is an illustrative diagram of a prior art stent;

FIG. 2 is a perspective view of an example stent according to exampleembodiments of the present invention;

FIG. 3 is a flattened view of the example stent of FIG. 2, according toexample embodiments of the present invention;

FIG. 4 is a cross sectional view of a covered stent device according toexample embodiments of the present invention;

FIG. 5 is a perspective view of the covered stent device of FIG. 4according to example embodiments of the present invention;

FIG. 6 is a graph depicting the median foreshortening values that weremeasured for various covered stent devices according to embodiments ofthe present invention that were built and tested; and

FIG. 7 is a flattened view of a stent similar in design to the stent ofFIGS. 2 and 3, which was tested for purposes of comparison, according toaspects of the present invention.

DETAILED DESCRIPTION

An illustrative embodiment of the present invention relates to a stenthaving a structural design that greatly reduces foreshorteningsubsequent to or during expansion to an operational diameter. Assupported herein by test results from sample stents according toembodiments of the present invention that were reduced to practice,foreshortening values of about 0% or less were achieved, whilemaintaining low values of recoil.

In particular, a stent according to an illustrative embodiment of thepresent invention can include a plurality of generally cylindricalrings, each formed of a plurality of substantially repeating bentsegments. The rings can be arranged in a series along a longitudinalaxis in such a way that each ring in the series is substantially amirror image of an immediately adjacent ring. The rings can beinterconnected by a plurality of interconnecting members, which can bearranged in rows that extend longitudinally along the stent. Eachinterconnecting member can include an elongate portion extending betweentwo coupling ends. The interconnecting members can assume a firstorientation or a second orientation that is substantially a mirror imageof the first orientation. The interconnecting members can be coupled tothe rings at midpoints of the bent segment. Along each row, consecutiveinterconnecting members alternate between the first orientation and thesecond orientation.

FIGS. 2 through 7, wherein like parts are designated by like referencenumerals throughout, illustrate example embodiments of a stent andmethods of making the same, according to the present invention. Althoughthe present invention will be described with reference to the exampleembodiments illustrated in the figures, it should be understood thatmany alternative forms can embody the present invention. One of skill inthe art will appreciate different ways to alter the parameters of theembodiments disclosed, such as the size, shape, or type of elements ormaterials, in a manner still in keeping with the spirit and scope of thepresent invention.

FIG. 2 depicts a perspective view of a stent 210 according to an exampleembodiment of the present invention. FIG. 3 depicts a top view of thestent 210 in a flattened (unrolled) state. The stent 210 includes aplurality of generally cylindrical, independently expandable rings 212arranged in a series along a longitudinal axis 224. Each of the rings212 can have a center point lying on the longitudinal axis 224, suchthat all of the rings 212 arc coaxial. The plurality of rings 212 cancollectively form an elongate, generally cylindrical shape. Each ring212 includes a plurality of substantial peaks 214 a and substantialvalleys 214 b arranged in an alternating fashion, such that eachsubstantial peak 214 a is adjacent two substantial valleys 214 b andeach substantial valley 214 b is adjacent two substantial peaks 214 a. Atransition region 228 adjoins every substantial peak 214 a to itsadjacent valleys 214 b, and adjoins every substantial valley 214 b toits adjacent substantial peaks 214 a. Accordingly, each substantial peak214 a is adjoined with a transition region 228 on each side, which leadsto an adjacent substantial valley 214 b. Similarly, each substantialvalley 214 b is adjoined with a transition region 228 on each side,which leads to an adjacent substantial peak 214 a. The transitionregions 228 can be unbent or bent. In FIG. 2, only three rings 212 aredepicted for clarity. In FIG. 3, six rings 212 are illustrated. It willbe appreciated by one of skill in the art that more or less rings 212can be included in the stent 210.

In addition to substantial peaks 214 a and substantial valleys 214 b,the rings 212 are also formed of larger repeating units, herein referredto as substantially repeating bent segments 222. Each of the pluralityof substantially repeating bent segments 222 includes one substantialpeak 214 a and one substantial valley 214 b, and a transition region 228adjoining the two. In the example embodiment of FIG. 2, the stent 210includes six substantially repeating bent segments 222. However, feweror greater numbers of substantially repeating bent segments 222 can beincluded depending on the particular intended application and dimensionsof the target deployment site. It should be noted that the phrase“substantially repeating” in the present application is well understoodby those of skill in the art to indicate that the units are repeating,but could accommodate a minor interruption in the repeating pattern.That is, the present invention is not intended to be limited to astrictly and exactly repeating pattern of bent segments. Should a stentbe constructed that replicates the repeating bent segment patterndescribed and claimed herein, but for one or several minor interruptionsto the pattern, such a stent would be considered to fall within thescope of the present invention.

In the example embodiment of FIGS. 2 and 3, each ring 212 is a mirrorimage of any ring 212 adjacent to it in the series. Accordingly, for anytwo adjacent rings 212, the substantial peaks 214 a of one of the twoadjacent rings 212 are circumferentially aligned with (e.g., are facing)the substantial valleys 214 b of the other of the two adjacent rings212, and vice versa. Said differently, the substantial peak 214 a andthe substantial valley 214 b of each of the substantially repeating bentsegments 222 are a mirror image of a substantial peak 214 a andsubstantial valley 214 b of a corresponding substantially repeating bentsegment 222 of an immediately adjacent ring 212. In alternativeembodiments, each successive ring 212 is not only a mirror image, butfurther is an angularly displaced mirror image. For example, each ring212 can be “turned” relative to its adjacent rings 212 by some amount ofangular displacement. The amount of angular displacement by whichsuccessive rings 212 are turned can be substantially uniform across theentire stent 210. In some embodiments, a covering process is used tocover the stent 210 which imparts a slight angular displacement to thesuccessive rings 212.

The rings 212 are interconnected and fixedly secured to one another by aplurality of interconnecting members 216. Each interconnecting member216 joins two adjacent rings 212. Each interconnecting member 216includes two coupling ends 218 and an elongate portion 220. For eachinterconnecting member 216, the elongate portion 220 extends between andadjoins the two coupling ends 218. As one non-limiting example, thecoupling ends 218 each can be an elbow (e.g., a generally “L” shapedmember), as depicted in the example embodiment of FIGS. 2 and 3. Eachcoupling end 218 is adjoined with a ring 212 at a substantiallyrepeating bent segment 222 at the midway point of a substantiallyrepeating bent segment 222 (i.e., on the transition region 228 half waybetween the substantial peak 214 a and the substantial valley 214 b of asubstantially repeating bent segment 222). For example, if the rings 212generally form a sinusoidal shape defined by the equation y=A*sin(x),then the interconnecting members 216 can join with the rings 212 at thepositions corresponding to zero-crossing points in the equation. Theinterconnecting members 216 and the rings 212 both can have a relativelythin, generally rectangular cross section (e.g., with rounded edges).

In contrast to the stent 110 of FIG. 1, each interconnecting member 216of the stent 210 of FIGS. 2 and 3 is in an “up-up” configuration or a“down-down” configuration, such that the coupling ends 218 of a singleinterconnecting member 216 extend to the same side (e.g., to the top orthe bottom, respectively) of the elongate portion 220, for substantiallyevery interconnecting member 216 included in the stent 210. Saiddifferently, the two coupling ends 218 of every individualinterconnecting member 216 extend circumferentially in the samedirection (e.g., clockwise or counter-clockwise). Furthermore, in theexample embodiment of FIGS. 2 and 3, the number of interconnectingmembers 216 between any two adjacent rings 212 is equal to the number ofsubstantially repeating bent segments 222 in each ring 212.

The two coupling ends 218 of each interconnecting member 216 of theexample of FIGS. 2 and 3 are azimuthally or circumferentially aligned,such that a straight line connecting the two coupling ends 218 isparallel to the longitudinal axis 224. Accordingly, the two couplingends 218 can be connected at corresponding mirror-image locations alongsubstantially repeating bent segments 222 on adjacent rings 212.Furthermore, each interconnecting member 216 can be situated such thatits length is substantially parallel to the longitudinal axis 224. Theinterconnecting members 216 form a plurality of rows 230 (see FIG. 3),each of which is substantially parallel to the longitudinal axis 224.The rows 230 extend longitudinally along the stent 210 and are equal innumber to the number of substantially repeating bent segments 222included in one ring 212.

The circumferential direction of orientation of the two coupling ends218 of each interconnecting member 216 can vary for successiveinterconnecting members 216 along each row 230. In the exampleembodiment of FIGS. 2 and 3, the interconnecting members 216 of anysingle row 230 are arranged in an alternating fashion, such that theinterconnecting members 216 alternate successively between the “up-up”configuration and the “down-down” configuration. Said differently, thedirectional orientation of the coupling ends 218 of successiveinterconnecting members 216 in a row 230 alternates between a firstorientation wherein the coupling ends 218 point in a clockwise directionand a second orientation wherein the coupling ends 218 point in acounterclockwise direction. The first orientation and the secondorientation (e.g., “up-up” and “down-down”) are substantially mirrorimages of each other. In the example embodiment of FIG. 3, theinterconnecting members 216 situated between any two adjacent rings 212are all in the same configuration (“up-up” or “down-down”), such thatall of the coupling ends 218 situated between any two adjacent rings 212point in the same circumferential direction (e.g., clockwise orcounter-clockwise).

Each of the interconnecting members 216 can have a variable, non-uniformwidth. Preliminary tests have suggested that such a feature of variablewidth of the interconnecting members 216 can strengthen the stent 210and prevent foreshortening when deployed with a cover. For example, theelongate portion 220 can include a slight bulge at its center, such thatthe central width of the elongate portion 220 of the interconnectingmembers 216 is the widest position of the interconnecting member 216. Inone example embodiment, the width at the center of the elongate portion220 is about 1.5 times the size of the width at the coupling ends 218 ofthe interconnecting members 216. As further non-limiting example, theratio of the largest width to the smallest width of the interconnectingmembers 216 can be about 1.56.

For each ring 212, each of the plurality of bent segments 222 can have asubstantially uniform width. Furthermore, all substantial peaks 214 a,substantial valleys 214 b, and transition regions 228 of a ring 212 canhave substantially the same substantially uniform width. It has beendiscovered that providing the substantially repeating bent segments 222with the same uniform width does not increase the foreshortening of thestent 210 during expansion with a cover. This is beneficial because suchuniform widths enable the stent 210 to achieve a smaller diameter andmore uniform crimping into a prolapsed state.

In addition, the peak-to-valley amplitude is uniform across each ring212. The peak-to-valley amplitude of each ring 212 can be uniform acrossall of the rings 212 or can vary across the rings 212. For example, twosuccessive rings 212 in the stent 210 can have peak-to-valley amplitudesthat are different from one another. The “peak-to-valley” amplitude isherein defined to have its normal definition as would be appreciated byone of skill in the art of the height of a substantially repeating bentsegment 222 as measured vertically from the substantial peak 214 a tothe substantial valley 214 b. It has been found that varying thepeak-to-valley amplitude (e.g., varying the value of the peak-to-valleyamplitude of the stent 210 or varying the peak-to-valley amplitude ofparticular rings 212 in the stent 210) can impact foreshorteningcharacteristics of the stent 210. Thus, the peak-to-valley amplitude canbe optimized as will be appreciated by one of skill in the art uponreading the present specification.

In accordance with one example embodiment of the present invention, thestent 210 is encapsulated in a cover, so as to form a covered stentdevice 242. For example, an illustrative embodiment of the covered stentdevice 242 is depicted in FIG. 4. More specifically, FIG. 4 depicts thestent 210 of FIG. 3 encapsulated in a cover 240 and depicted from across-sectional view along line A-A of FIG. 3. The cover 240 includes anouter layer 240 a disposed on the exterior face of the stent 210 and aninner layer 240 b disposed on an interior face of the stent 210. Theouter and inner layers 240 a, 240 b are constructed of a single piece ofmaterial, e.g., which has been “cuffed” around the edge of the stent 210so as to form the outer and inner layers 240 a, 240 b.

FIG. 5 depicts the covered stent device 242 of FIG. 4 from a perspectiveview. As can be seen, the stent 210 is hidden from view, as it isentirely encapsulated by the cover 240. The covered stent device 242generally can be included in any number of different delivery devicesand systems, e.g., for treatment of stenosed vessels. As just onenon-limiting and illustrative example, the covered stent device 242 canbe included in a balloon dilation catheter assembly, as will be readilyappreciated by one of skill in the art.

Example 1

An example of the covered stent device 242 that was built and testedwill now be described with reference to FIG. 6. In particular, FIG. 6depicts an example method that was used to build a plurality of coveredstent devices 242. In the Example 1 provided herein, the cover 240 wasconstructed of expanded polytetrafluoroethylene (ePTFE).

The ePTFE cover was provided, having a desired diameter. The ePTFE coverwas constructed according to conventional methods known to those ofskill in the art (forming a PTFE tube, sintering the PTFE tube, etc.).The stent 210 according to FIGS. 2 and 3 was constructed and provided,having a desired diameter. The stent 210 was manufactured usingconventional manufacturing techniques known to those in the art (lasercutting, electropolishing, etc.). In the example provided herein, thestent 210 was constructed from type 316 LVM stainless steel.

In the example provided herein, the small overlapping portion wassituated near a center of the length of the stent 210. However, asdescribed previously herein, the small overlapping portion alternativelycan be situated at a position away from a center of the length. It hasbeen found that displacing the overlapping portion from the center ofthe length of the stent 210 and nearer to one end of the stent 210 inthis manner produces slower expansion of the resultant covered stentdevice at that particular end during deployment of the resultant coveredstent device. Said differently, the small overlapping portion of theePTFE cover can be used to restrict the expansion rate of portions ofresultant covered stent device, e.g., thereby achieving greater timingcontrol of expansion. Thus, depending on the particular geometry of theaffected target site (e.g., of the intima and/or of the lesion beingtreated), it may be desirable in certain embodiments to position theoverlapping portion of the ePTFE cover at a non-central longitudinalposition so as to desirably affect the rate of expansion of theresultant covered stent device at that particular longitudinal position.In such embodiments, a non-central portion of the resultant coveredstent device expands at a different (e.g., controlled or predetermined)rate or in a different amount than a remaining portion of the resultscovered stent device.

In particular, different groups of covered stent devices 242 weremanufactured, generally distinguishable by length. In one group, alength of 16 mm was provided. In a second group, a length of 24 mm wasutilized. The groups of stents were tested for performancecharacteristics, and their performance data was measured. This data ispresented in Table I, below.

TABLE I Foreshortening and Recoil Data Initial Expanded Initial MeanMean Diameter Diameter* Length Foreshortening Recoil 1.6 mm 5 mm 16 mm0.20% 8.60% 1.6 mm 5 mm 24 mm −0.70% 8.00% 1.7 mm 6 mm 16 mm 2.80% 7.20%1.7 mm 6 mm 24 mm 0.50% 7.40% 1.8 mm 7 mm 16 mm 6.80% 6.00% 1.8 mm 7 mm24 mm 3.70% 5.90% *indicates diameter to which the covered stent devices242 were expanded and the diameter at which the covered stent devices242 were measured for foreshortening and recoil results

In general, all of the covered stent devices 242 represented in Table I,above, were constructed to include six substantially repeating bentsegments 222 per ring 212. Each row in Table I represents data for asample of fifteen substantially identical covered stent devices 242, The16 mm covered stent devices 242 were constructed to include six rings212. The 24 mm covered stent devices 242 were constructed to includenine rings 212. As presented in Table I, in some instances,foreshortening values of 0.20% were measured. In other instances,negative foreshortening values were measured, which indicate that thecovered stent device 242 actually elongated during or upon expansion.

In all tests, the covered stent devices 242 were expanded to anoperational deployment diameter. An “operational deployment diameter,”as described herein, refers to a diameter at which the stent can beoperably deployed (expanded) for at least one target site. The data ofTable I are further presented in a graph in FIG. 6. Specifically, thegraph of FIG. 6 displays the median values of foreshortening achievedfor each covered stent device 242 as grouped by length. Accordingly,each foreshortening curve in FIG. 6 shows foreshortening characteristicsexhibited for the covered stent devices 242 across a particulardeployment diameter range for a particular initial length of the coveredstent devices 242.

One of skill in the art will appreciate alternative ways to constructthe covered stent devices 242 Furthermore, it should be understood thatthe dimensions selected for testing are illustrative and in no waylimiting. Similarly, one of skill in the art will appreciate that thenumber of substantially repeating bent segments 222 to be included perring 212 can depend on required crimping profiles, which depends onintended medical application, intended target sites, etc. The number ofrings 212 to include can depend on the particular desired length. Stillother features may be modified as will be appreciated by one of skill inthe art upon reading the present specification.

In addition, many alternatives and modifications to the stent 210 arepossible and will be appreciated by one of skill in the art. Forexample, rather than providing that all rings 212 of the stent 210 havethe same substantially uniform peak-to-valley amplitude, one or more ofthe rings 212 can have a substantially uniform peak-to-valley amplitudethat is different from the substantially uniform peak-to-valleyamplitude of an adjacent ring 212. Still other alternatives arepossible. However, one of skill in the art will appreciate that suchalternatives (while acceptable and contemplated within the scope of thepresent invention) were not specifically tested and thus may not exhibitthe described performance characteristics (e.g., recoil and/orforeshortening characteristics). Those of skill in the art willappreciate that seemingly minor structural differences in the latticestructure of a stent can have substantial impact on the operational andperformance characteristics of that stent. As such, alternative designsto the structure described herein that are considered to fall within thescope of the present invention will have operational and performancecharacteristics similar to those of the present design.

Example 2

For comparative purposes, a plurality of comparative stents 250 having aslightly different structure from the stent 210 of FIGS. 2 and 3 werecovered using the same methodology and subsequently tested forperformance. Specifically, the design of the comparative stents 250 usedin this example is depicted in FIG. 8 in a flattened, rolled-out state.To ensure that the comparative stents 250 provided for a fair comparisonwith the covered stent devices 242, the comparative stents 250 weretested for performance prior to covering, i.e., as bare metal stents. Inparticular, foreshortening and recoil of the comparative stents 250 whenuncovered was measured. This data is presented in Table II, below. Ascan be seen, the comparative stents 250 performed with minimalforeshortening and recoil when uncovered and serving as bare metalstents. In particular, the average foreshortening values were as low as1.1% in some instances.

TABLE II Results for uncovered comparative stents 250 Initial ExpandedInitial Mean Mean Diameter Diameter* Length Foreshortening Recoil 1.6 mm5 mm 16 mm 1.1% 6.6% 1.6 mm 5 mm 24 mm −0.5% 6.4% 1.7 mm 6 mm 16 mm 2.2%6.5% 1.7 mm 6 mm 24 mm 2.6% 7.0% 1.8 mm 7 mm 16 mm 11.0% 6.7% *indicatesdiameter to which stents were expanded and the diameter at which theuncovered comparative stents 250 were measured tor foreshortening andrecoil results

Each row in Table II represents data for a sample of either two or threesubstantially identical comparative stents 250. Once the effectivenessof the design characterizing the comparative stents 250 was generallyestablished (e.g., through the tests of the comparative stents 250 asbare metal stents), additional groups of the comparative stents 250 werecovered using the same method. Subsequent to covering the comparativestents 250, the covered comparative stents 250 were subjected to thesame foreshortening performance tests. In particular, foreshortening ofthe covered comparative stents 250 was measured. The resulting data ispresented in Table III, below.

TABLE III Results for covered comparative stents 250 Initial ExpandedInitial Mean Diameter Diameter* Length Foreshortening 1.6 mm 5 mm 16 mm7.74% 1.6 mm 5 mm 24 mm 6.03% 1.7 mm 6 mm 16 mm 17.17% 1.7 mm 6 mm 24 mm13.08% 1.8 mm 7 mm 16 mm 29.64% *indicates diameter to which stents wereexpanded and the diameter at which the covered comparative stents 250were measured for foreshortening results

In the tests, the covered comparative stents 250 represented in TableIII were expanded to an operational deployment diameter of about 5 mm,about 6 mm, or about 7 mm. Each row in Table III represents data for asample of either fifteen or sixteen substantially identical coveredcomparative stents 250. As presented in Table III, mean foreshorteningvalues of almost 30% were measured for the covered comparative stents250 having an initial length of 16 mm that were expanded to a diameterof about 7 mm. For comparison, the 16 mm length stent design of thepresent invention utilized in Example 1 resulted in foreshorteningvalues of about 6.8% when expanded to an operational deployment diameterof about 7 mm.

Thus, the stent design of the inventive covered stent devices 242 ofExample 1 exhibited performance that demonstrated significantly lessforeshortening amounts relative to the stent design of the examplecovered comparative stents 250 utilized in Example 2 when covered. Thesesignificantly different results were unexpected given the minorstructural difference between the design of the covered comparativestents 250 and the design of the covered stent devices 242 according toembodiments of the present invention. As such, the data provided hereinindicates that the covered stent devices 242 according to exampleembodiments of the present invention perform at surprising andunexpected performance levels (e.g., as measured by foreshortening). Oneof skill in the art will appreciate the data presented herein representssignificant and notable improvement over the art.

Numerous modifications and alternative embodiments of the presentinvention will be apparent to those skilled in the art in view of theforegoing description. Accordingly, this description is to be construedas illustrative only and is for the purpose of teaching those skilled inthe art the best mode for carrying out the present invention. Details ofthe structure may vary substantially without departing from the spiritof the present invention, and exclusive use of all modifications thatcome within the scope of the appended claims is reserved. Within thisspecification embodiments have been described in a way which enables aclear and concise specification to be written, but it is intended andwill be appreciated that embodiments may be variously combined orseparated without parting from the invention. It is intended that thepresent invention be limited only to the extent required by the appendedclaims and the applicable rules of law.

It is also to be understood that the following claims are to cover allgeneric and specific features of the invention described herein, and allstatements of the scope of the invention which, as a matter of language,might be said to fall therebetween.

What is claimed is:
 1. A stent device, comprising: a plurality ofgenerally cylindrical rings each formed by a plurality of repeating bentsegments, each of the plurality of bent segments comprising a peak, avalley, and a transition region extending between the peak and thevalley, each bent segment having a midpoint on the transition regionsubstantially midway between the peak and the valley, the plurality ofrings being arranged in a series along a longitudinal axis in such a waythat the peak and the valley of each bent segment of each ring in theseries is substantially a mirror image of a peak and a valley of acorresponding curved segment in an immediately adjacent ring; aplurality of interconnecting members connecting one of the plurality ofrings to an adjacent ring of the one of the plurality of rings, each ofthe plurality of interconnecting members comprising: a first couplingend; a second coupling end opposite the first coupling end; and anelongate portion extending between the first coupling end and the secondcoupling end, wherein the first coupling end, the elongate portion, andthe second coupling end combine in a first orientation or a secondorientation, wherein the second orientation is substantially a mirrorimage of the first orientation; and an expanded polytetrafluoroethylene(ePFTE) material cover encapsulating the stent device; wherein the firstcoupling end intersects with the midpoint of the transition region of abent segment of the one of the plurality of rings and the secondcoupling end intersects with the midpoint of a bent segment of theimmediately adjacent ring of the plurality of rings; wherein theplurality of interconnecting members are arranged in rows extendinglongitudinally along the device; and wherein along each of the rows theinterconnecting members alternate with each consecutive occurrencebetween the first orientation and the second orientation; and wherein acentral width of at least one elongate portion of the plurality ofinterconnecting members is the largest width of the interconnectingmember and a width of at least one of the coupling ends is the smallestwidth of the interconnecting member.
 2. The device according to claim 1,wherein the first coupling end and the second coupling end of each ofthe plurality of interconnecting members each comprise an elbow.
 3. Thedevice according to claim 1, wherein the number of interconnectingmembers between any two adjacent rings of the plurality of rings isequal to the number of repeating bent segments in each ring of theplurality of rings.
 4. The device according to claim 1, wherein thefirst coupling end and the second coupling end of each of the pluralityof interconnecting members are azimuthally aligned.
 5. The deviceaccording to claim 1, wherein the first coupling end and the secondcoupling end of each of the plurality of interconnecting members arecircumferentially aligned.
 6. The device according to claim 1, whereineach of the plurality of rings is independently expandable in a radialdirection.
 7. The device according to claim 1, wherein the plurality ofrepeating bent segments forms a generally sinusoidal pattern.
 8. Thedevice according to claim 1, wherein a peak-to-valley amplitude issubstantially equal for each of the plurality of rings.
 9. The deviceaccording to claim 1, wherein each of the plurality of bent segments hasa substantially uniform width.
 10. The device according to claim 1,wherein the plurality of rings are constructed from one or more of anon-biodegradable alloy, stainless steel, or cobalt chromium.
 11. Thedevice according to claim 1, wherein when the covered stent device isexpanded up to an operational deployment diameter then the deviceexhibits a foreshortening of about 6% or less.
 12. The device accordingto claim 1, wherein when the covered stent device is expanded up to anoperational deployment diameter then the device exhibits aforeshortening of about 2% or less.
 13. The device according to claim 1,wherein when the covered stent device is expanded up to an operationaldeployment diameter then the device exhibits a foreshortening of about0% or less.
 14. The device according to claim 1, wherein the stentdevice with a cover exhibits a recoil of about 6.6% or less when thecovered stent has an initial diameter of 1.6 mm and an expanded diameterof 5 mm.
 15. The device according to claim 1, wherein the material covercomprises an inner layer and an outer layer, and wherein when expandedto an operational deployment diameter, the covered stent device exhibitsforeshortening of about 6% or less.
 16. A method of manufacturing astent device, the method comprising the steps of: providing a pluralityof generally cylindrical rings each formed by a plurality of repeatingbent segments, each of the plurality of bent segments comprising a peak,a valley, and a transition region leading between the peak and thevalley, each bent segment having a midpoint on the transition regionsubstantially midway between the peak and the valley, the plurality ofrings being arranged in a series along a longitudinal axis in such a waythat the peak and the valley of each bent segment of each ring in theseries is substantially a mirror image of a peak and a valley of acorresponding curved segment in an immediately adjacent ring; andproviding a plurality of interconnecting members connecting one of theplurality of rings to an adjacent ring of the one of the plurality ofring, each of the plurality of interconnecting members comprising: afirst coupling end; a second coupling end opposite the first couplingend; and an elongate portion extending between the first coupling endand the second coupling end, wherein the first coupling end, theelongate portion, and the second coupling end combine in a firstorientation or a second orientation that is substantially a mirror imageof the first orientation; and encapsulating the stent device with anexpanded polytetrafluoroethylene (ePFTE) material cover; wherein thefirst coupling end intersects with the midpoint of the transition regionof a bent segment of a ring of the plurality of rings and the secondcoupling end intersects with the midpoint of a bent segment of adifferent and immediately adjacent ring of the plurality of rings;wherein the plurality of interconnecting members is arranged in rowsextending longitudinally along the device; and wherein along each of therows the interconnecting members alternate with each consecutiveoccurrence between the first orientation and the second orientation, andwherein a central width of at least one elongate portion of theplurality of interconnecting members is the largest width of theinterconnecting member and a width of at least one of the coupling endsis the smallest width of the interconnecting member.
 17. The methodaccording to claim 16, wherein the first coupling end and the secondcoupling end of each of the plurality of interconnecting members eachcomprise an elbow.
 18. The method according to claim 16, wherein thenumber of interconnecting members between any two adjacent rings of theplurality of rings is equal to the number of repeating bent segments ineach ring of the plurality of rings.
 19. The method according to claim16, wherein the first coupling end and the second coupling end of eachof the plurality of interconnecting members are azimuthally aligned. 20.The method according to claim 16, wherein the first coupling end and thesecond coupling end of each of the plurality of interconnecting membersare circumferentially aligned.